Chapter 10 Computing plant height
10.1 Introduction
Plant height is not very well simulated for the moment. It is computated using the plant width, which depends itself on the plant lai (lai+eai+laisen). Please see Chapter 2 for more details. Figure 10.1) shows the simulated height of wheat in Auzeville, and the variables from which it is computed.
Figure 10.1: Simulated height compared to the observed values, and variables from which it is computed from, in a self-intercrop of Wheat-Wheat
The plant height is important in the case of intercrops because it has high impact on the light interception of both species. Indeed, a sensitivity analysis was performed using the sticRs package on the parameter that links the lai to the height: P_rapforme. The results are shown below (see html version of this book for interactivity):
height_sensi= sticRs::load_sensi(dirpath = "data/rapforme_sensitivity")
if(knitr:::pandoc_to() == "html") {
gg_objects=
lapply(height_sensi$gg_objects,
function(x){
plotly::ggplotly(x, tooltip= "group")
})
htmltools::tagList(gg_objects)
}else{
multiplot(plotlist = height_sensi$gg_objects)
}As we can see on the above plots, as the plant height is affected, its lai is also impacted afterwards. We can also see that no values of P_rapforme gave satisfactory plant height, so maybe the link between the plant lai and the plant height is not as straightforward as previously thought, and maybe there is another variable that could be better correlated to it.
10.2 Link between height and lai and dry mass
Using the observations from Auzeville, we plotted the evolution of the plant height through time along the lai and the masec (i.e. dry mass) to see if and how they are correlated. The Figure 10.2) shows this evolution with standardized and linearly interpolated observed values for all variables to make it easier to compare.
Figure 10.2: Observed plant height compared to the lai and dry mass for both wheat and pea in sole crop. Values are standardized for comparison
The Figure 10.2) shows that the plant height is better correlated to the masec than to the lai. We propose to use the masec to compute it rather than the lai.